Intraocular pressure monitoring/measuring apparatus and method

ABSTRACT

An apparatus and method of monitoring/measuring intraocular pressure in an eye includes a miniature pressure sensor having an attachment for connecting the miniature pressure sensor to the iris of the eye or an intraocular lens. The miniature pressure sensor is preferably a Polysilicon Resonant Transducer (PRT).

RELATED APPLICATIONS

This application is a Continuation under 35 U.S.C. 111(a) ofPCT/US00/03269, filed Feb. 8, 2000 and published as WO 00/45693 A3 onAug. 10, 2001, which is a continuation-in-part of U.S. Ser. No.09/246,379, filed Feb. 8, 1999 (U.S. Pat. No. 6,193,656), whichapplications are incorporated herein and made a part hereof byreference.

FIELD OF THE INVENTION

The present invention relates to an intraocular pressuremeasuring/monitoring apparatus and method thereof and more particularlyto an in situ intraocular pressure monitoring/measuring apparatus andmethod thereof.

BACKGROUND OF THE INVENTION

The American Academy of Ophthalmology has reported that about twomillion people in the United States have primary open angle glaucoma(the most common of several types of glaucoma). About seven millionoffice visits are made each year by people with glaucoma or thosesuspected of having glaucoma. Glaucoma is the second leading cause oflegal blindness in the United States and the leading cause of legalblindness in African-Americans. About 80,000 people in the United Statesalone are legally blind from glaucoma, not counting those with lesservisual impairment.

By definition, glaucoma is a group of eye diseases characterized by anincrease in intraocular pressure which causes pathological changes inthe optic disc and nerve fiber layer of the retina with resultanttypical defects in the field of vision. The relationship betweenglaucoma and intraocular pressure is fundamental to proper treatmentplanning for glaucoma.

Normal intraocular pressure is considered to be less than 22 mm Hg.However, at least one in six patients with glaucoma may have pressurebelow this normal level and yet still have progressive eye damage. Also,at any single test, about one half of all glaucoma patients will exhibitmeasured intraocular pressures below 22 mm Hg but actually will haveaverage intraocular pressures higher than 22 mm Hg. This makes frequenttesting necessary to obtain an accurate assessment of a patient'saverage intraocular pressure.

Most current methods of routine intraocular pressure measurements relyon applanating a plunger against the cornea. The degree to which aportion of the cornea is deformed indicates the pressure inside the eyeresisting this deformation. All of these methods are inferring theintraocular pressure rather than measuring it directly. Some specialistsbelieve that the thickness of the cornea can vary from person to person,and that other factors such as corneal scars or previous surgery mayaffect the accuracy of these measurements. Also, most of these methodsrequire that topical anesthesia be placed on the cornea prior tomeasuring the pressure and the measurements be made by trainedpersonnel. Therefore, there is a need to develop techniques to makerepeated and/or continuous measurements and to enable persons other thantrained personnel to make such measurements.

U.S. Pat. No. 5,005,577 discloses an intraocular lens pressuremonitoring device based on radiosonde technology. Radiosonde technologyhas been around for decades. The idea of using radiosonde technology forintraocular pressure monitoring was proposed in the '577 patent.However, it is unknown from the '577 patent how to make or use such anintraocular pressure monitoring device to carry out the invention.Specifically, the technology disclosed in the '577 patent has not beenminiaturized in such a way to make it possible to insert into the eye.

Further, the '577 patent discloses an intraocular lens pressuremonitoring device as a part of an integrated intraocular lens system,not a stand-alone device. If replacement of the monitoring device isneeded, it would be difficult to separate the device from the lenswithout major surgery.

The '577 patent also discloses active sensors. An active sensor usuallyincludes a power supply and a transmitter. As indicated in the '577patent, an active sensor is generally too large in size to be implantedin the eye. Although it is speculated that technology will progress tothe point to allow an active sensor to be implanted in the eye, thepatentee does not, in fact, know what technology may be used and how itcould be used to resolve the above-mentioned problems and addresses theabove-mentioned concerns.

Accordingly, there is a need for a miniaturized device capable ofinserting into an eye to monitor/measure intraocular pressureaccurately, frequently, and continuously. There is also a need for astand-alone intraocular pressure monitoring/measuring device separatefrom an intraocular lens system.

SUMMARY OF THE INVENTION

The present invention relates to an intraocular pressuremeasuring/monitoring apparatus and method thereof, and more particularlyto an in situ intraocular pressure monitoring/measuring apparatus andmethod thereof.

The present invention discloses a miniature apparatus capable ofmonitoring intraocular pressure in an eye. The apparatus includes aminiature pressure sensor having an attachment for connecting the sensorto a site in the eye. For example, the sensor can be attached to thefront surface of the periphery of the iris, accomplished by suturing,clamping, and the like, or incorporated into an intraocular lens forimplantation at the time of cataract surgery.

In one aspect of the present invention, the pressure sensor is aPolysilicon Resonant Transducer (PRT) or a similarly suitabletransducer. PRT technology allows accurate intraocular pressuremeasurements. Further, the apparatus using PRT technology is smallenough to allow implantation into the eye without impeding eye function.In the present invention, the PRT can be encased in materials such assilicone, acrylic polymer, polymethylmethacrylate (PMMA) and the like.These materials have been used to make intraocular lenses and are provensafe for implantation into the eye.

In one embodiment of the present invention, the PRT is a fullyself-contained, stand-alone device. The PRT is operated by irradiatingit with laser light. The PRT resonates to this light in such a way thatis indicative of the pressure of the environment in which it resides.The resonance of the reflected laser light is proportional to theambient pressure surrounding the device, e.g. within the eye.Alternatively, if the PRT is placed behind the iris, e.g. proximate toan intraocular lens, or as a part of an intraocular lens implant.non-visible wavelengths of light can be used. These frequencies of lightwill penetrate the tissue of the iris and interact with the device tomonitor/measure the intraocular pressure.

In another aspect of the present invention, the PRT apparatus can beplaced in the eye as an outpatient procedure, as an office procedure, oras a part of a cataract surgery. This technique will provide directintraocular pressure measurements.

In another aspect of the present invention, the pressure sensor, e.g., aPRT, can be incorporated into a wide variety of surgical or non-surgicalinstruments that can be inserted into the body of a mammal, such as ahuman, such as, for example, laproscope, optical fiber laser device,scalpel, endoscope, phacoemulsification handpiece, irrigation/aspirationhandpiece, catheter and the like. In particular, these instruments couldbe used to monitor temperature, acoustic energy and pressure directly inthe eye.

An advantage of the present invention is that the pressure measurementscan be taken at any time without the need for a topical anesthesia or atrained person. The measurements can be taken by the patients themselvesat home. A further advantage is that the present invention allowscontinuous measurements throughout the day or night, and even through aclosed eyelid. This would allow therapy to be tailored to the patient'sneeds. Moreover, the effect and timing of glaucoma medications can bemonitored much more efficiently than through the use of traditionaltechniques.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the construction and operationalcharacteristics of a preferred embodiment(s) can be realized from areading of the following detailed description, especially in light ofthe accompanying drawings in which like reference numerals in theseveral views generally refer to corresponding parts.

FIG. 1 is a front outside view of an eye for which an intraocularpressure monitoring/measuring apparatus in accordance with the presentinvention can be adapted.

FIG. 2 is a cross-sectional inside view of the eye for which theintraocular pressure monitoring/measuring apparatus can be adapted.

FIG. 3 is an enlarged perspective view of an intraocular pressuremonitoring/measuring apparatus incorporated into an intraocular lens.

FIG. 4 is an enlarged elevational view of the intraocular pressuremonitoring/measuring apparatus incorporated on a lens' haptic.

FIG. 5 is an enlarged front elevational view of the intraocular pressuremonitoring/measuring apparatus to be attached to an iris of the eye.

FIG. 6 is an enlarged side elevational view of the intraocular pressuremonitoring/measuring apparatus with a barb for attaching the apparatusto the iris of the eye.

FIG. 7 is an enlarged side elevational view of the intraocular pressuremonitoring/measuring apparatus with a locking clamp for attaching theapparatus to the iris of the eye.

FIG. 8 is an enlarged side elevational view of the intraocular pressuremonitoring/measuring apparatus with suturing strings for attaching theapparatus to the iris of the eye.

FIG. 9 is a front outside view of the eye with the intraocular pressuremonitoring/measuring apparatus attached on the iris.

FIG. 10 is a cross-sectional inside view of the eye with the intraocularpressure monitoring/measuring apparatus attached on the iris.

FIG. 11 is a partial outside view of the eye with the intraocularpressure monitoring/measuring apparatus attached on the iris.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The miniature apparatus of the present invention is capable ofmonitoring intraocular pressure in an eye. The apparatus includes aminiature pressure sensor having an attachment for connecting the sensorto a site in the eye. The apparatus may be a passive (i.e. no powersource), miniature electronic circuit such as an integrated circuit chipwith a sensor component for interaction with optic, electromagnetic,sonic, or other energy forms. The circuit also includes a pressuredetecting component that changes circuit response as a function ofpressure.

In the following description of the exemplary embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration the specific embodiment in which theinvention may be practiced. It is to be understood that otherembodiments may be made without departing from the scope of the presentinvention.

Referring now to FIGS. 1 and 2, there is generally illustrated majorcomponents of an eye 100 including an iris 102, a natural crystallinelens 104, a cornea 106, a pupil 108, a retina 110, and an optic nerve112. An intraocular pressure monitoring/measuring apparatus adapted inthe eye will be discussed below.

FIG. 3 is an enlarged perspective view of an intraocular pressuremonitoring/measuring apparatus or pressure sensor 200 incorporated intoan intraocular lens 202, such as a typical polymethylmethacrylate (PMMA)intraocular lens. The intraocular lens 202 may be inserted into the eyein place of the natural crystalline lens 104 in FIG. 1 at the time of acataract surgery. Similar intraocular lenses can be made of silicone,acrylic or PMMA, etc. The intraocular pressure monitoring/measuringapparatus 200 can be a polysilicon resonant transducer (PRT). Forillustrative purposes, the PRT 200 is shown in FIGS. 3-11. The PRT 200may be incorporated into the edge of the lens 202 itself (FIG. 3) oronto one of arms (haptics) 204 used for fixating the lens 202 in thecenter of the eye after implantation into the eye. The majority ofintraocular lenses 202 are implanted behind the iris 102 where thenatural crystalline lens 104 once resided. However, the intraocular lens202 may also be implanted in front of the iris 102 in selected patients.

It is appreciated that if desired, the PRT 200 can be incorporated intoan eye with the natural crystalline lens 104 in place within the scopeof the present invention. It is also appreciated that for illustrativepurposes, the PRT 200 and the intraocular lens 202 are not shown in anormal scale. In a preferred embodiment, the intraocular lens 202 mayhave a diameter of 5.5-7.0 mm, and the PRT 200 may have one millimetersquare or less. It is appreciated that other suitable sizes may be usedwithout departing from the principles of the present invention.

FIGS. 5-8 illustrate various exemplary techniques of attaching the PRT200 onto an internal tissue, e.g. the iris 102. The PRT 200 may beconstructed to be enclosed in a housing 500 with eyelets 502, 504 forsuturing. The PRT 200 is disposed at a central region of the housing500. As mentioned above, the PRT 200 is preferably in a dimension of 1mm by 1 mm or less. The housing 500 may be made of silicone, acrylic orpolymethylmethacrylate (PMMA) materials. The housing 500 may beincorporated into the intraocular lens 202 as shown in FIG. 3 or 4.Alternatively, the housing 500 may be attached to the iris 102 bypassing suture materials 800 through the eyelets 502,504 of the housing500 as shown in FIG. 8.

Another attachment technique is shown in FIG. 6. A small barb 600resembling a fishing hook made of prolene (an inert suturing material)or a similar inert material may be attached to the PRT housing 500. Thebarb 600 may be used to impale the iris 102 allowing attachment of thePRT 200 onto the front surface of the iris 102.

A further attachment technique is shown in FIG. 7. A clamping device 700of similar material may also be used to crimp the PRT 200 around a smallportion of the iris tissue allowing attachment of the PRT 200 to theiris 102.

FIGS. 9-11 illustrate various exemplary locations for attachment of thePRT 200 to the iris 102. It is noted that the PRT 200 as shown is not toscale for better visualization. FIG. 9 shows that the PRT 200 isattached to the front of the periphery of the iris 102 at the sixo'clock position of a left eye. FIG. 10 shows that the PRT 200 isattached, by crimping the clamping device 700, around a portion of theiris 102 at the twelve o'clock position, while another attachment of asecond PRT 200 may be attached, by using the barb 600, to a portion ofthe iris 102 at the six o'clock position. It is noted that for bettervisualization, the PRT 200 is not drawn to scale or located peripherallyon the iris 102. FIG. 11 shows that the PRT 200 is located on theperiphery of the iris 102 at the three o'clock position in a right eyeas seen from the bridge of a nose.

In the above illustration, the apparatus 200 is preferably the PRT. ThePRT is a miniature device such that it can be implanted into the eye.The PRT is operated by irradiating it with laser light. The PRTresonates to this light in such a way that is indicative of the pressureof the environment in which it resides. The resonance of the reflectedlaser light is proportional to the ambient pressure surrounding thedevice, e.g. within the eye. Alternatively, non-visible wavelengths oflight can be used to penetrate the tissue of the iris. Use of thisalternative allows placement of the PRT behind the iris, e.g. proximateto an intraocular lens, or as a part of an intraocular lens implant.

The theory for the PRT device can be found in an article by Zook et al.,entitled “Optically Excited Self-Resonant Microbeams”, published inSensors and Acuators A 52 (1996), pages 92-98; or an article by Burns etal., entitled “Sealed-Cavity Resonant Microbeam Pressure Sensor”,published in Sensors and Acuators A 48 (1995), pages 179-186. Briefly,highly modulated reflected light is produced by an interferometricstructure composed of a microresonator and vacuum enclosure. This allowsremote fiber-optic excitation and readout of the microbeam resonancefrequency for single-point or multi-point sensing. The self-resonantconfigurations of a PRT device which use optics eliminate physicalwiring to the outside and eliminate external circuitry required tomaintain microbeam resonance. A PRT device is operated by irradiatingthe PRT device with a laser light. The PRT device resonates to the lightin such a way that is indicative of the pressure of the environment inwhich it resides. The resonance of the reflected laser light isproportional to the ambient pressure surrounding the device, e.g. withinthe eye. Alternatively, if the PRT device is placed behind the iris,e.g. proximate to an intraocular lens, or as a part of an intraocularlens implant, non-visible wavelengths of light can be used. Thesefrequencies of light will penetrate the tissue of the iris and interactwith the device to monitor/measure the intraocular pressure. It will beappreciated that other types of suitable transducers and/or pressuresensors can be employed.

The apparatus 200 is a self-contained device. As discussed above, it canbe fully encased in a material bio-compatible to the eye, such assilicone, acrylic, or polymethylmethacrylate (PMMA), and the like. Smallholes can be made on the edges of the encasement to allow a suture to bestrung thus attaching the apparatus 200 to the iris or other sites ofthe eye. Alternatively, a small clamp, preferably of the same materialas the encasement, can be incorporated into the encasement. This allowsthe edge of the encasement to be clamped to the iris by simply crimpingthe clamp around some of the iris tissue. The attachment, such assuturing and clamping and using the prolene barb, is known in the art.It will be appreciated that other attachment embodiments can be usedwithout departing from the principles of the present invention.

The apparatus 200 can be used as a stand-alone device by attaching theapparatus to the eye. It will be appreciated that the apparatus can alsobe used as a part of an intraocular lens implant as shown in FIGS. 3 and4. In such a case, the apparatus and the intraocular lens can bearranged in a single unit.

The pressure sensor can also be incorporated into a wide variety ofsurgical or non-surgical instruments that can be inserted into the bodyof a mammal, such as a human, such as, such as, for example, alaproscope, an optical fiber laser device, a scalpel, an endoscope, aphacoemulsification handpiece, a irrigation/aspiration handpiece,catheter and the like. In particular, these instruments could be used tomonitor temperature, acoustic energy and pressure directly in the eye.

The gauge pressure to be monitored/measured by the apparatus 200preferably ranges from 0 to 80 mm Hg. Pressure accuracy is preferablywithin 1 mm Hg. Operating temperatures are optimally from 97° F. to 104°F. The laser is preferably a class II laser in red to near infraredwavelength.

In clinical applications, one advantage of the present invention is thatit allows direct, accurate measurements of the intraocular pressure.Furthermore, pressures can be taken by shining a medically safe laser orother compatible non-visible light source onto the apparatus or the irisoverlying the apparatus without having to touch the eye. This eliminatesuser variability in intraocular pressure measurements and allowspatients to take pressure measurements at home. Further, no eye drops orpuffs of air are necessary. Pressures may be measured with the eyelidsclosed, thus allowing 24-hour monitoring of intraocular pressures.Accordingly, the present invention allows development of diurnalintraocular pressure curves and thus making possible drug efficacycomparisons. It will be appreciated that there are many alternative usesof the present invention. For example, a PRT or other device similarlyplaced inside the eye could be used in conjunction with an externallaser (or other light, electromagnetic, sonic, etc.) source forspectroscopic or similar analysis of the aqueous (fluid inside the frontpart of the eye). This may yield measurements of components of theaqueous such as levels of glucose, protein, electrolytes and the like.Since the aqueous of the eye is an ultrafiltrate of the blood and sincelevels of these components in the aqueous vary with levels of thesecomponents in the blood, such a device may be used for monitoring bloodglucose levels in diabetic patients without the need for drawing blood,as an example. Levels of other components of the blood may similarly beimplied, calculated or measured.

The preferred embodiment of the present invention has been described indetail. It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. An apparatus capable of monitoring intraocular pressure in an eye having an internal tissue, comprising: an optic energy source disposed external to the eye; and an optically resonate pressure sensor having an attachment for connecting the pressure sensor to the internal tissue of the eye, wherein upon activating the pressure sensor by the optic energy source, the pressure sensor monitoring/measuring the intraocular pressure in the eye.
 2. The apparatus of claim 1, wherein the energy source is a laser source.
 3. The apparatus of claim 1, further comprising an intraocular lens, wherein the pressure sensor is incorporated into the intraocular lens.
 4. An apparatus capable of monitoring intraocular pressure in an eye having internal tissue, comprising an optically resonate integrated circuit pressure sensor and an attachment adapted to connect the pressure sensor to the internal tissue of the eye.
 5. The apparatus of claim 4, wherein the pressure sensor is encased in a material biocompatible to the eye.
 6. The apparatus of claim 5, wherein the attachment includes a sensor encasement with holes therethrough for suturing the apparatus onto the internal tissue of the eye.
 7. The apparatus of claim 5, wherein the attachment is a clamp for holding the pressure sensor onto the internal tissue of the eye.
 8. The apparatus of claim 5, wherein the attachment is a prolene barb for attaching on the iris.
 9. The apparatus of claim 5, wherein the pressure sensor is encased in the material made of silicone.
 10. The apparatus of claim 5, wherein the pressure sensor is encased in the material made of polymethylmethacrylate (PMMA).
 11. The apparatus of claim 5, wherein the pressure sensor is encased in the material made of acrylic polymer.
 12. The apparatus of claim 4, wherein the pressure sensor includes polysilicon.
 13. The apparatus of claim 4, further comprising an intraocular lens, wherein the pressure sensor is incorporated into the intraocular lens.
 14. The apparatus of claim 4, wherein the pressure sensor is small enough to allow implant into the eye without impeding eye function.
 15. The apparatus of claim 4 wherein the pressure sensor is a passive, miniature electronic circuit having a sensor component for interaction with optic energy and a pressure detector component for affecting circuit response.
 16. A method of monitoring intraocular pressure in an eye having an internal tissue, comprising: attaching a laser resonate integrated circuit pressure sensor to the internal tissue of the eye; irradiating a laser light onto the pressure sensor; and sensing intraocular pressure in the eye.
 17. The method of claim 16, wherein the attaching of the pressure sensor is accomplished by suturing.
 18. The method of claim 16, wherein the attaching of the pressure sensor is accomplished by clamping.
 19. The method of claim 16, wherein the attaching pressure sensor is accomplished by using a prolene barb.
 20. The method of claim 16, further comprising implanting an intraocular lens in the eye, wherein the pressure sensor is a stand-alone device separate from the intraocular lens.
 21. The method of claim 16, further comprising implanting an intraocular lens in the eye, wherein the pressure sensor is a part of the implanted intraocular lens. 